低功耗低相位噪声4．8GHz CMOS压控振荡器芯片设计

Design of a 4.8-GHz low power dissipation and low phase noise CMOS VCO

采用TSMC0．181μm RFCMOS工艺设计并实现了一个应用于无线传感器网络射频前端频率综合器的低功耗、低相位噪声4．8GHz电感电容压控振荡器。此振荡器的核心电路采用电流源偏置的互补差分负阻结构，降低了电路对电源电压变化的灵敏度和功耗。电感电容谐振腔采用了降低相位噪声的设计方法。在不恶化相位噪声性能的前提下，核心电路还采用3比特的开关电容阵列提高了振荡器的频率调谐范围。测试结果表明，在电源电压为1．8V时，此振荡器的频率调谐范围可达20％，可有效克服因电源波动、工艺角偏差以及温度变化等而引起的偏差；振荡频率为4．8GHz时，频偏为3MHz处的相位噪声为-121．68dBc／Hz。芯片带焊盘面积为700μm×900μm。核心电路仅消耗1．5mA电流。

A 4.8-GHz low power dissipation and low phase noise LC vohage-controlled oscillator （VCO） for wireless sensor networks was designed and implemented based on the TSMC 0.18μm RF CMOS process. The complementary differential negative resistance LC oscillator structure was adopted to achieve the low power dissipation. The core circuit was biased by current to reduce the sensitivity to power supply and to further decrease the power dissipation. The LC tank was carefully designed to lower the phase noise. A 3-bit switch capacitor array was adopted to provide a large tuning range without worsening the phase noise performance. The VCO was tested under a supply voltage of 1. 8V and the results demonstrated that its whole tuning range achieved 20%, and the offset due to the variations of power supply, process corner and temperature was perfectly compensated. The phase noise of -121.68 dBc/Hz was obtained at 3 MHz offset with the carrier of 4.8GHz. The chip area is 700μm × 900μm with pads and the operating current of the core circuit is only 1.5mA. Key words： voltage-controlled oscillator （VCO）, low power dissipation, low phase noise, LC tank design, wireless sensor networks （WSN）